1. Technical Field
The present disclosure relates to Ni-Fe-W-P alloys and a method and apparatus for depositing same.
2. Background of Related Art
Chromium plating offers unique deposit properties, including brightness, discoloration stability at atmospheric conditions and long preservation of the luster. But uniformity of the deposits is poor, the required current density is high, current efficiency is low, and the cost of energy is great. At the same time, chromium ions are very poisonous. Any chromium mist that escapes or direct drainage of waste water containing chromium ions can greatly contaminate atmosphere and water sources, adversely affecting the health of humans.
It would be desirable to provide the beautiful color and luster, good corrosion resistance and excellent wear resistance such as those of chromium deposits without the aforementioned shortcomings. Many substitutes for chromium deposits have been investigated and developed, of which, up to now, Sn-Co alloy seemed to be the most promising. See, U.S. Pat. Nos. 3,966,564 and 3,951,760, the disclosures of which are incorporated herein by reference.
Compared with chromium plating deposits, Sn-Co alloy deposits have the following advantages:
1. Sn-Co alloy deposits have the same excellent luster and beautiful color as chromium deposits and can be used as decorative deposits. PA1 2. Corrosion resistance of Sn-Co alloy deposits is superior to that of chromium deposits and can be used as advanced protection deposits. PA1 3. Sn-Co alloy deposits have good adhesion, excellent toughness, low internal stress, no porosity and no cracks. PA1 4. Dispersing and penetrating abilities are very good. Throwing and covering power are very good. PA1 5. Current efficiency of Sn-Co alloy plating is one to four times higher than that of chromium plating. PA1 6. Because Sn-Co alloy plating is not poisonous, draining waste gas and water can be easily handled.
But the hardness of Sn-Co alloy deposits is about HV 500-600 and wear resistance is only one half that of chromium plating deposits.
In order to overcome the disadvantages of Sn-Co alloy various alloy plating deposits have been developed as substitutes. For example, U.S. Pat. No. 4,529,668 discloses a W-Co-B electrodeposition alloy.
U.S. Pat. No. 5,614,003 discloses electroless deposition of Ni-Mo-P, Ni-Cu-P, Ni-Sn-P, Co-W-P and Ni-W-P combinations. These coatings have high hardness, good wear resistance and good corrosion resistance, but suffer from such problems as low current efficiency and high energy cost. For example, the electrodeposition rate of W-Co-B is only about 1.6 .mu.m-50 .mu.m per six hours at a solution temperature of 72-86.degree. C.
In order to overcome these disadvantages of prior known deposition compositions and methods the present method has been developed.